Laser Light Sources in Digital Projectors Highlights
The first projectors utilized incandescent lamps as their light source. Despite advances in every other area of display technology, this fact is basically unchanged. Today’s digital units still rely on a hot-running ultra-high pressure lamp to create an image. In addition to their short lifespan and high cost, they dim and shift color as they age. There has to be a better way!
A few years ago, LEDs were put forth as an alternative light source. They’re still available in a few expensive models. At this year’s CEDIA Expo, Epson introduced two laser projectors, the LS10000 and LS9600e. They’re not the first of their kind but they are the first to sell for less than $10,000. We hope this breakthrough will encourage other manufacturers to follow suit in embracing this exciting new tech.
Today we look at the history of the laser, how it works and how it’s used in the latest front projectors.
Laser Light Sources in Digital Projectors Highlights Summary
- Projectors have long been saddled with old tech in the form of incandescent lamps.
- Though other components have evolved to create better images, the lamp is essentially unchanged.
- Lasers provide a reliable cool-running light source that lasts upwards of 20,000 hours and doesn’t dim or degrade with age.
- Epson is the first manufacturer to market a laser projector for under $10,000.
Introduction – A New Hope
At this year’s CEDIA Expo in Denver, Colorado; Epson introduced something new and unexpected – the LS10000 and LS9600e laser projectors. Since the advent of film projection in 1879, we have relied on various types of incandescent light sources as the means to create images on the screen. These sources all share one major disadvantage, they degrade and wear out in a relatively short time requiring an expensive replacement.
Incandescent bulbs come in many flavors but no matter what the technology, they all produce light by either heating a metal filament to a white hot temperature or creating an electrical arc inside a gas-filled glass bulb. Obviously no matter what material is used, it will eventually burn out and need replacement. When projecting a large image over a substantial distance; as you would in a commercial cinema, you need a lot of light and with that comes heat.
When projectors were first designed for home use, the problem of which light source to use was no less difficult to solve. Interestingly however, if you set aside film, the first video projectors suitable for smaller rooms were based on the cathode-ray tube. Just like the televisions of our youth (of mine anyway, I’m 48), the CRT creates light by firing electrons at a glass panel coated with phosphor. In a color system, three different phosphors are used to represent the primary colors – red, green and blue.
In a sense CRT guns are like light bulbs but since nothing is actually burning, they last much longer than the two or three thousand hours of an average UHP lamp.
That brings us to what most of us deal with today. Modern digital projectors are based on one of three imaging technologies, DLP, LCoS or LCD and they all require a light source to work their magic. In virtually every digital video projector sold today that means an ultra-high pressure (UHP) lamp.
These lamps are like fancy light bulbs. Filled with mercury, they strike an electric arc that vaporizes the gas to produce light. Despite a relatively small size, outputs of 250 watts are possible. Like all incandescent technologies however, they have a limited lifespan. Most projectors quote times in the range of 2,000-3,000 hours. In practice however, bulbs can dim significantly in just 1,000 hours.
So far, we have two alternatives to the UHP lamp – LED and laser. LED has already appeared in several high-end models from Runco and others and is a viable way to eliminate bulb changes. Q-series projectors have a claimed lifespan of 30,000 hours – enough to watch six hours per day for over 13 years.
The technology we’ll be focusing on today is laser; or more accurately laser diode. The Epson LS10000 uses two such diodes along with a phosphor wheel and a reflective three-chip imager to produce its picture. This is a big deal because it’s the first projector we’ve seen with an alternative light source selling for less than $10,000. In fact it’s only $8000. Let’s take a closer look at the history of the laser and how it has the potential to revolutionize your home theater.
A Brief History Of The Laser
The word laser conjures up all sorts of images from science fiction. Before the laser was even invented we had Buck Rogers’ famous ray-gun. We first saw a believable implementation of laser tech in the 1966 TV series Star Trek with its famous Phaser weapon. And who could forget the blasters and light sabers from Star Wars? All of these images suggest a weapon or cutting tool; and real lasers can be used for those purposes. But there are many more applications for them in industry, medicine and now, home theater.
The theoretical foundation for the modern laser was first proposed by Albert Einstein in 1917 when he modified Max Planck’s Law of Radiation. Without going into an explanation worthy of a Nobel Laureate; his theories relate to the stimulated emission of electro-magnetic radiation. A subset of this is the amplification of light.
The first practical application was called the Maser, which stands for “Microwave Amplification by Stimulated Emission of Radiation”. It was a device built in 1953 that could amplify microwaves. Today, we benefit from this breakthrough every time we use a GPS or an air traffic controller consults his radar screen. It easily followed that a device to amplify visible light couldn’t be too far behind.
The first functioning laser appeared in 1960. It was a red-type that used a ruby crystal to produce a pulsed beam of 694 nanometers or 694 billionths of a meter (that’s really small). From there progress was rapid. Shorter wavelengths and greater power made it possible to project beams of high intensity; so high they could cut through metal.
Today lasers are used in numerous applications from guiding bombs to their targets to reading the microscopic pits and lands on a Blu-ray or CD. While we haven’t quite made it up to Buck Rogers’ raygun, the technology has certainly come a long way in only 50 years.
How Lasers Work
Laser is an acronym that stands for “Light Amplification by Stimulated Emission of Radiation”. The simplest explanation is to say it is a device that amplifies and focuses light into a powerful and narrow beam. By doing this, energy can be concentrated into an extremely fine point. If you think of how a lens can focus sunlight tightly enough to start a fire, you can start to understand what’s going on.
In a typical laser, there is a diode which produces light at a single wavelength using two sandwiched semi-conductors called a diode. Applying current to them excites electrons to recombine into photons. These photons are then passed through a collimating lens to keep them in a straight line. Thus a single color of light is produced that remains focused into a narrow beam over a great distance. Depending on the amount of current used, the beam can be more or less intense. And the light’s wavelength or color is determined by the chemical composition of the semi-conductors.
Lasers have very high spatial and temporal coherence. Spatial means the beam will remain focused over a long distance. This is why laser pointers are possible. It’s actually quite amazing to see just how far you can project the dot from one. In fact, people have gotten in trouble when they pointed them at low-flying aircraft.
Temporal coherence means that the beam is narrow enough to emit a single wavelength of light; or in layman’s terms, a single color. This is where we get the violet lasers found in Blu-ray players or the red lasers used to read barcodes. Violet has a shorter wavelength and therefore a narrower beam. That’s why it can read discs with greater data density. And even though a Blu-ray player uses a violet laser, it’s pretty easy to see why the industry didn’t go with the trademark “Violet-ray”.
For the LS-series projectors, Epson has chosen to use two laser diodes along with a phosphor wheel. The phosphor is there to ensure not only accurate color but to prevent any variation in the laser’s output from appearing on the screen as dimming or flickering. If you’ve heard the term “laser speckle”, that’s what the phosphor wheel prevents. It also spreads the light to properly cover the imaging chips which are far larger than the laser’s beam.
To increase output, Epson uses two lasers in their projectors; one for red and green and one for blue. Why not a laser for each primary color? It comes down to economics. Both diodes are blue; one excites a phosphor that creates yellow light (for the red and green primaries) and the other remains blue by using a neutral phosphor.
Because lasers operate at specific visible wavelengths, a larger color gamut is possible. In the case of the LS-series, you can go a little bigger than Adobe RGB. Of course in today’s film content the largest gamut you’ll see is DCI (Digital Cinema Initiative). In the chart above, it’s denoted by the light blue line; about halfway between sRGB and Adobe RGB. This is the gamut used in commercial digital cinemas; you won’t find it on consumer Blu-ray discs. It’s possible that will change in the near future so it’s nice to know the LS-10000 is ready to match tomorrow’s home theater standards.
Lamp Technologies And How The Laser Fits In
Since the earliest days of film projection, incandescent bulbs have been used as the light source. While this technology has progressed greatly in the areas of efficiency and service life, it’s pretty much the same in terms of what goes on inside the glass.
To produce light a UHP lamp strikes an arc inside a chamber filled with mercury vapor. As the mercury heats up and vaporizes, it emits light. This is the type of bulb used in nearly every home theater projector sold today. In larger commercial projectors, xenon arc lamps are used. The principal is the same; you just get a lot more light.
Incandescent bulbs have several disadvantages; the two principal ones being a relatively short service life and the production of heat.
While large mercury-vapor lamps can last upwards of 20,000 hours, you’d have to have a bulb the size of a street lamp to accomplish this. Obviously home theater projectors require more efficient packaging. Many manufacturers rate their lamps at 2,000 to 3,000 hours. In my experience, there can be sufficient degradation in output to require replacement at 1000 hours.
UHP lamps start to dim as soon as they are first installed. Depending on how bright it was to begin with, you may lose half your output by the time the bulb is changed. Not only that, its color changes too. Typically, a projector bulb will become redder as it ages. If color accuracy is important to you, re-calibration every 250-300 hours is recommended.
On top of this there is the problem of heat. All incandescent bulb technologies produce heat as they do their thing. In a film projector, the heat is enough to burn the film if it stops for more than a brief moment. In a digital model, that heat can destroy a delicate silicon imaging chip or melt a DLP device.
The only way to combat this is with carefully thought out cooling systems. Fans are the easiest way to keep things from melting and they work very well. But there is noise associated with any air-cooling solution. Modern projectors have progressed greatly in this area by using ultra-quiet motors and internal baffles to keep the rush of air to a minimum.
Before we move on, here’s a quick tip. All home theater owners know that if the power fails while the projector is on it won’t be able to cool the bulb after it shuts down. At best this can shorten its lifespan and at worst it can actually cause an explosion (that’s really bad). We recommend installing a UPS (battery backup) between your projector and the wall. That way when the power goes out, you have a few minutes to shut it down properly.
There has to be a better way right? Runco and others thought so when they introduced LEDs in a few of their models. This technology promised real relief to the high heat and short lifespan of UHP lamps. We covered several promising models at the CEDIA Expo in 2010 and reviewed the Q750i in September of that year. Prices were quite high then; on the order of $15,000 and up. Unfortunately, this is still the case and the choices have dwindled to two models from Runco and a couple from Sim2, Digital Projection and Christie. And yes, they’re still five figures.
Price is not the only obstacle to throwing away our incandescent lamps once and for all. There is the problem of output. LEDs just don’t produce the brightness of UHP. For now, LED projectors will be relegated to small theaters because they just don’t have enough power to light up a large screen at throw distances over 15 feet. If you have more than 10 seats and your screen exceeds 120 inches, LED probably won’t cut it.
Epson’s New LS-series Projectors
The LS9600e and LS10000 are the first projectors we’ve seen for under $10,000 that have a light source other than UHP. In fact the LS10000 is selling for $8,000. This undercuts LED by at least $2,000 and hopefully will inspire others to follow suit. So besides a lower price, what else does Epson bring to the table with its shiny new models?
We’ve already mentioned lifespan. A laser-equipped projector like the LS10000 is rated for a 30,000 hour service life. You could feasibly use it as your primary display and get 20 years out of it with no trouble. During that time, its output would not decrease and its color would not shift.
Secondly lasers generate far less heat than their incandescent counterparts. Heat is an issue in any bulb projector because it can damage imaging chips or bulbs can literally explode if they are not constantly cooled. Since a laser runs more efficiently, fans can turn slower and therefore more quietly. And there’s no need to run the fan after a viewing session. If your power goes out during a movie, you won’t reduce your bulb life by skipping the cool-down cycle.
The biggest thing represented by Epson’s LS-series models is their price breakthrough. Remember when I mentioned the still-five-figure price-tags of LED projectors? That doesn’t seem likely to change any time soon. Manufacturers of mid and low-priced products have shown no interest in LED and thanks to the economics of scale; prices for that technology seem likely to remain high.
Epson has introduced the LS10000 flagship model at a price of $8,000. Basically, you’re getting all the advantages of LED with a little more light output, a larger color gamut, better contrast, all at less cost.
I was able to see it in action at the CEDIA Expo in Denver and came away impressed. It has more than enough light output to fill a 120-inch screen from 15 feet and its image quality was easily on par with the best JVC models. Enthusiasts know that contrast is king and Epson has been nipping at JVC’s heels for some time now. Thanks to lasers’ fast modulation capability, there is no need for an iris. Even though the LS’s native contrast is excellent, the picture gained more depth with the dynamic contrast turned on. And I could see no evidence of detail crush or image pumping.
It all seems like a fantasy come true; and it may very well be so. I am anxiously awaiting my opportunity to put an LS10000 through its paces for a Secrets review. The day it arrives at my door, expect to hear a shout of glee from the direction of Florida.
Other Laser Displays
It may sound like Epson is the only manufacturer with laser projection but they are not alone. A quick Google search reveals that Sony has been shipping a business-class model since 2013, the VPL-FHZ55.
It’s better suited for a boardroom or church than a home theater however. It puts out 4,000 lumens from a 3LCD light engine which means its contrast is not quite up to home theater standards. It also lacks an HDMI input. It does have a 20,000 rated lifespan however and comes in a package about the size of JVCs D-ILA models.
Many of you may remember Mitsubishi Laservue. This was the first use of lasers in a consumer display that I know of. It was found in a line of rear-projection televisions that were sold from 2008-2012. Like Epson and Sony, its laser is used to excite a phosphor which produces light. Recently, the Laservue name was resurrected to describe the backlight in a new 4K flat panel prototype seen at various shows in 2013. It hasn’t turned into a shipping product as of yet but perhaps we’ll see it someday.
The problem Mitsubishi ran into is a common one – lasers made their HDTVs too expensive. The rear projection models were commanding around $6,000 for a 75-inch screen. While well-heeled enthusiasts are willing to pony up for high-end displays, the masses are not.
In commercial applications, lasers are set to potentially up the light output ante for 3D projection. Early in 2014, Christie and Barco previewed models that can pump out an astounding 60,000 lumens. These projectors use six pure lasers and can actually meet the 14 foot-Lambert SMPTE standard in 3D on a screen 23 meters wide, amazing! Oh and did I mention they’re 4K? With most digital theaters lucky to get four fL on the screen in 3D, this is a major piece of news. Unfortunately only a few one-percenters will be able to get one of these for the home because they cost around $350,000 and are the size of a coffee table.
Christie is making an effort to bring lasers home however. At CEDIA I saw a single-chip DLP model using a laser-phosphor design. I wasn’t able to view a demo but was told it would sell for around $15,000.
Conclusions: What Happens Next?
For now it seems only Epson is making a serious effort to make laser projection into an affordable home theater solution. It will likely own the sub-$10K market for the foreseeable future while Christie remains popular with commercial and high-end home theaters. What does this mean for the enthusiast? Well we know that Epson licenses its 3LCD technology to Panasonic. It is quite possible they will do the same with its laser engine. Getting lasers into more projectors can only mean two things – competition will stimulate advancement and drive prices down.
The obstacle to all this is the relatively small market for front projection compared to flat panels. When LED backlights first appeared in HDTVs, it took only a single model generation for them to nearly kill off the cold-cathode florescent tube. We hoped this would happen when LEDs migrated to projectors but thanks to their tiny volume (we’re talking about thousands versus millions in unit sales) it hasn’t happened nor is it likely to.
I’d like to think there is hope for the laser because it’s coming in at a lower price level. Plus Epson is the largest home theater projector manufacturer at present. Their large sales volume coupled with a new technology could be the formula for mass-adoption. All we can do now is to wait for the market to absorb and process it.
I’d love to see a great first sales year for the LS-series followed by more model introductions next year. Perhaps they could shed a few features like lens memories or 4K scaling to get lasers into a sub-$5,000 model. I think once that happens, you’ll see other manufacturers (JVC, are you listening?) hop on the ferry.
There’s little doubt that any projector owner would love to give up their hot and expensive bulbs for a little science fiction tech in their theater. To have the ease of use and maintenance that a television user enjoys is a dream that just might be coming true.
While I have yet to get my hands on an LS10000, please stay tuned to these pages because when I do, rest assured it will get a thorough hands-on evaluation. The laser projector shows incredible promise. Soon we’ll know if that promise is genuine.